266 APPENDIX TO THE 



as Prof. King appears to question the correctness of some of our statements 1 it will be 

 desirable to represent, side by side (in PL LIV) those forms that appear to be common 

 to the Carboniferous and Permian deposits of our island. 



Carboniferous Names. Permian Names. 



Terebratula sacculus, Martin, sp. 1809. Terebratula sufflata, Schlotheim, sp. 

 Dav., pi. liv, fig. 5. 1816. Dav., pi. liv, fig. 6. 



The identity of the Carboniferous and Permian shell is so complete that Schlotheim's 

 denomination will require to be located among the synonyms of S. sacculus. Prof. King 

 admits this identity. 



Terebratula hastata, Sow., sp. 1824. ? Terebratula elongata, Schlotheim, sp. 

 Dav., pi. liv, figs. 1 and 3. 1816. Dav., pi. liv, figs. 2 and 4. 



It is an unquestionable fact that many specimens of the Carboniferous and Permian 

 shells are undistinguishable, as will be at once perceived by a glance at the specimens 

 or figures selected from among others for illustration ; but I must confess that more 

 difference is shown between the greater number of typical T. hastata and T. elongata 

 than is here represented, the strong resemblance being the exception, and more especially 

 observable between that variety of T. hastata we have termed Gillingensis and T. elongata 

 proper. It must also be observed, that it is often impossible to distinguish certain 

 examples of T. sacculus and T. hastata, which appear to merge the one into the other, 

 and the same may be said with reference to T. sufflata and T. elongata, and this proves 

 how intimately connected are all the British forms of Carboniferous and Permian Tere- 

 bratula. The subject relating to the identity of T. hastata and T. elongata may therefore, 

 for the present, remain an open question. 



Athyris Royssii, L' JEveille, sp. 1835. Dav., Athyris pectinifera, /. de C. Sow., 1840. 

 pi. liv, fig. 8. Dav., pi. liv, fig. 9. 



M. De Verneuil and Prof. King have both alluded to the resemblance which appears 

 to exist between these shells ; and although I thought at one time that sufficient differences 

 might perhaps be established between them, I am now very much afraid that they will 

 have to be merged into a single species, and, if so, Sowerby's denomination would require 

 to give way to that of L'Eveille. A. pectinifera does not appear to have attained the 

 large proportions of a full grown A. Rogssii, but size alone cannot be made use of as a 

 distinguishing character between species which otherwise resemble each other, and in the 



1 King, "On certain species of Permian Shells said to be found in Carbouiferons Rocks," ' Edinburgh 

 Philosophical Journal,' vol. xiv, new series, p. 37, &c, 1861, and vol. xv, April, 1862. 



